The invention relates to a device for connecting fixedly in terms of rotation two components arranged coaxially in one another, for example a shaft to a hub, by means of a tapered piston shiftable axially in a tapered slot for selective connection and disconnection of the two components. A device of this type is known form WO 84/04367 (U.S. Patent Specification No. 4,616,948).
In specific types of the known device, the two pressure chambers on the end faces of the conical annular space and of the tapered annular piston are supplied with pressure medium from one end face of the device. This purpose is served by axially directed ducts, one of which is arranged within a wall of the device, extends over virtually the entire length of the conical annular chamber and opens into the rear pressure chamber. For this, it is necessary to drill a very deep duct, and it can happen that the drill deviates obliquely from the intended drilling direction, especially when high-strength material is used. It therefore becomes unavoidable to make the wall of the drilled-through sleeve disproportionately thick to take account of directional errors in drilling. At the weakest point of the rear pressure chamber, the wall thickness corresponds approximately to 3 times the diameter of the cut. This results in large external dimensions of the device and consequently of the rotational connection as a whole, and also results in centering inaccuracies when the bore to the rear pressure chamber runs very close to the cylindrical surface of the annular chamber.
The torque which can be transmitted by the device depends on the useful axial length of the device and therefore also on the length of the annular piston. Consequently, with the device having a specific outside diameter, the useful length of the piston and therefore of the device is restricted by the second duct drilled up to the rear pressure chamber.
The annular piston of the known device has axially or spirally arranged grooves on its outer and on its inner cylindrical surface. These grooves serve for distributing lubricant between the surfaces touching one another, in order to produce a smooth axial movement of the annular piston during the supply of pressure to one of the pressure chambers and radial tension on the hub and shaft. Furthermore, these grooves also serve for distributing the pressure exerted by the pressure medium over the entire inner and outer cylindrical surface of the annular piston. As a result, there is also a radial expansion of the device and the piston moves more easily.